1. Field of the Invention
The present invention relates to compositions based on heat-vulcanizable diorganopolysiloxane resins and containing iodine, to dosage forms shaped therefrom and adapted for the controlled release of iodine values, and to a process for treating domestic water supplies and beverages utilizing such compositions/dosage forms.
2. Description of the Prior Art
The number of subjects exhibiting a deficiency or an inadequacy of iodine is currently estimated at several hundred million worldwide. The geographical regions affected to the greatest degree are Latin America, particularly along the Andean Cordillera, and virtually all the non-coastal regions of Africa and of Asia (Pakistan, India, Nepal, China, Laos, etc.).
The principal pathological consequences of iodine deficiency are well known. These are essentially, on the one hand, goiter and its complications, among which may be included swallowing disorders, respiratory disorders, cancer, peripheral circulation and, on the other hand, hypothyroidism and its complications, among which may be mentioned: cretinism, cerebral disorders, premature births, miscarriages and congenital abnormalities.
While iodine deficiency has disappeared from industrialized countries because, for example, the salts used for cooking are iodized, this is not the case in the developing countries, where the two main campaigns undertaken to date have proven ineffective.
These campaigns have for their focus, on the one hand:
(i) the iodination of cooking salt: this is not effective in the majority of the developing countries because very frequently the consumption of salt is minimal, the systems for the distribution of salt via the economic and commercial networks are virtually nonexistent and, finally, in a tropical region, iodine which is added to salt escapes rapidly if it is not perfectly packaged; PA1 (ii) the intramuscular injection of iodinated oil: this injection has the advantage of exhibiting a delayed action, but it is not devoid of disadvantages, particularly the risks of infection, the risks of iodine allergy, and the risks of hyperthyropidism or of hypothyroidism, which are caused by the injection of a necessarily supraphysiological dosage. PA1 (A) a diorganopolysiloxane resin containing at least two vinyl groups bonded to silicon per molecule and having a viscosity of at least 500,000 mPa.s at 25.degree. C,; PA1 (B) at least one organohydropolysiloxane containing at least three hydrogen atoms bonded to silicon per molecule; PA1 (C) a reinforcing filler; PA1 (D) a catalytically effective amount of a catalyst which is a compound of a metal of the platinum group; and PA1 (E) at least one organic and/or inorganic iodine compound in solid or liquid form at ambient temperature, soluble in water and nontoxic. PA1 (a) the nature of the iodine compound; PA1 (c) the concentration of the iodine compound within the matrix; PA1 (d) the surface/volume ratio R of the module. PA1 (i) g of from 1 to 300 .mu.m; PA1 (ii) t of from 10 to 100 parts by weight of iodine compound per 100 parts of (A); and PA1 (iii) R of from 0.5 to 50 in the case of a cylindrical shape. PA1 (A) 100 parts of a diorganopolysiloxane resin containing at least two vinyl groups bonded to silicon per molecule and having a viscosity of at least 500,000 mPa.s at 25.degree. C.; PA1 (B) at least one organohydropolysiloxane containing at least 3 hydrogen atoms bonded to silicon per molecule, in such quantity that the ratio of the number of the hydride functions in (B) to the vinyl groups in (A) ranges from 0.4 and 10; PA1 (C) 5 to 130 parts of a reinforcing, preferably siliceous, filler selected from among pyrogenic silicas and precipitated silicas; PA1 (D) a catalytically effective amount of a catalyst which is a compound of a metal of the platinum group; and PA1 (E) 5 to 150 parts of an organic and/or inorganic iodine compound, solid at ambient temperature, soluble in water and nontoxic. PA1 (1) C.sub.1 -C.sub.5 alkyl radicals, substituted or otherwise by halogen atoms or cyano radicals, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, 3,3,3-trifluoropropyl, .beta.-cyanoethyl and .tau.-cyanopropyl radicals,; PA1 (2) C.sub.2 -C.sub.4 alkenyl radicals such as vinyl, allyl and 2-butenyl radicals; and PA1 (3) C.sub.6 -C.sub.8 monocyclic aryl radicals, substituted or otherwise by halogen atoms, such as phenyl, chlorophenyl, tolyl and trifluoromethylphenyl radicals. PA1 (CH.sub.3).sub.2 SiO, PA1 CH.sub.3 (CH.sub.2 .dbd.CH)SiO, PA1 CH.sub.3 (C.sub.6 H.sub.5)SiO, PA1 (C.sub.6 H.sub.5).sub.2 SiO, PA1 CH.sub.3 (C.sub.2 H.sub.5)SiO, PA1 CH.sub.3 CH.sub.2 --CH.sub.2 (CH.sub.3)SiO, PA1 CH.sub.3 (n--C.sub.3 H.sub.7)SiO, PA1 (CH.sub.3).sub.3 SiO.sub.0.5, PA1 (CH.sub.3).sub.2 (CH.sub.2 .dbd.CH)SiO.sub.0.5, PA1 CH.sub.3 (C.sub.6 H.sub.5).sub.2 SiO.sub.0.5, PA1 CH.sub.3 (C.sub.6 H.sub.5)(CH.sub.2 .dbd.CH)SiO.sub.0.5, PA1 HO(CH.sub.3).sub.2 SiO.sub.0.5, PA1 CH.sub.3 O(CH.sub.3).sub.2 SiO.sub.0.5, PA1 C.sub.2 H.sub.5 O(CH.sub.3).sub.2 SiO.sub.0.5, PA1 n--C.sub.3 H.sub.7 O(CH.sub.3).sub.2 SiO.sub.0.5, PA1 HO(CH.sub.2 .dbd.CH)(CH.sub.3)SiO.sub.0.5.
and, one the other hand:
Furthermore, Belgian Patent BE-A-889,680 describes the introduction of oligoelements, including iodine, into the drinking water of ruminants, in the form of a dispersion in a binder such as, for example, plaster of Paris. A diorganopolysiloxane may be added with a view to slowing the diffusion of the oligoelement. In addition, the use of iodine and of iodine compounds for disinfecting or for purifying water is well known. Compare, for example, U.S. Pat. Nos. 2,347,567, 2,743,208 and 3,408,295.
There also exist very many patents describing the use of polymeric systems, especially silicone, for the controlled release of an active ingredient, for example by means of a transdermal system (U.S. Pat. No. 4,053,580), or by oral ingestion, especially for ruminants (French Patent FR-A-2,560,768).
Lastly, U.S. Pat. No. 4,384,960 describes placing iodine I.sub.2 tablets in a plastic bottle, into which water enters through a porous polymer membrane. The water dissolves the iodine. The purpose of the membrane is merely to prevent the iodine tablets from leaving the bottle.
It is simply suggested, furthermore, that it is possible to introduce iodine I.sub.2 into the bottle in a liquid dispersion of silicone or of a dimethylsiloxane elastomer, and then to cure them. This suggested solution is not technically feasible because, firstly I.sub.2 is a well-known inhibitor of the catalysts for curing silicone elastomers capable of being vulcanized at ambient temperature (see, in particular, the publication by W. D. Morain et al., Plastic and Reconstructive Surgery, 59, 2, 215-222 (1977) and, secondly, because of its high volatility, I.sub.2 sublimes during the crosslinking of silicone elastomers when heated.
However, in this system, not only is there no control over the release of iodine, but also the iodination of water takes place by noncontinuous or continuous addition of a few drops of highly iodized (to saturation) water contained in the bottle, to any receptacle containing untreated water. It is clear that the solution proposed by U.S. Pat. No. 4,384,960 is imperfect, especially because of the fact that it involves an individual method which, like the intramuscular injection of iodine, requires mass education and mobilization of entire populations.